1 // Copyright 2012-2015 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 //! A dynamically-sized view into a contiguous sequence, `[T]`.
13 //! Slices are a view into a block of memory represented as a pointer and a
18 //! let vec = vec![1, 2, 3];
19 //! let int_slice = &vec[..];
20 //! // coercing an array to a slice
21 //! let str_slice: &[&str] = &["one", "two", "three"];
24 //! Slices are either mutable or shared. The shared slice type is `&[T]`,
25 //! while the mutable slice type is `&mut [T]`, where `T` represents the element
26 //! type. For example, you can mutate the block of memory that a mutable slice
30 //! let x = &mut [1, 2, 3];
32 //! assert_eq!(x, &[1, 7, 3]);
35 //! Here are some of the things this module contains:
39 //! There are several structs that are useful for slices, such as [`Iter`], which
40 //! represents iteration over a slice.
42 //! ## Trait Implementations
44 //! There are several implementations of common traits for slices. Some examples
48 //! * [`Eq`], [`Ord`] - for slices whose element type are [`Eq`] or [`Ord`].
49 //! * [`Hash`] - for slices whose element type is [`Hash`].
53 //! The slices implement `IntoIterator`. The iterator yields references to the
57 //! let numbers = &[0, 1, 2];
58 //! for n in numbers {
59 //! println!("{} is a number!", n);
63 //! The mutable slice yields mutable references to the elements:
66 //! let mut scores = [7, 8, 9];
67 //! for score in &mut scores[..] {
72 //! This iterator yields mutable references to the slice's elements, so while
73 //! the element type of the slice is `i32`, the element type of the iterator is
76 //! * [`.iter`] and [`.iter_mut`] are the explicit methods to return the default
78 //! * Further methods that return iterators are [`.split`], [`.splitn`],
79 //! [`.chunks`], [`.windows`] and more.
81 //! *[See also the slice primitive type](../../std/primitive.slice.html).*
83 //! [`Clone`]: ../../std/clone/trait.Clone.html
84 //! [`Eq`]: ../../std/cmp/trait.Eq.html
85 //! [`Ord`]: ../../std/cmp/trait.Ord.html
86 //! [`Iter`]: struct.Iter.html
87 //! [`Hash`]: ../../std/hash/trait.Hash.html
88 //! [`.iter`]: ../../std/primitive.slice.html#method.iter
89 //! [`.iter_mut`]: ../../std/primitive.slice.html#method.iter_mut
90 //! [`.split`]: ../../std/primitive.slice.html#method.split
91 //! [`.splitn`]: ../../std/primitive.slice.html#method.splitn
92 //! [`.chunks`]: ../../std/primitive.slice.html#method.chunks
93 //! [`.windows`]: ../../std/primitive.slice.html#method.windows
94 #![stable(feature = "rust1", since = "1.0.0")]
96 // Many of the usings in this module are only used in the test configuration.
97 // It's cleaner to just turn off the unused_imports warning than to fix them.
98 #![cfg_attr(test, allow(unused_imports, dead_code))]
100 use core::cmp::Ordering::{self, Less};
101 use core::mem::size_of;
104 use core::slice as core_slice;
106 use borrow::{Borrow, BorrowMut, ToOwned};
110 #[stable(feature = "rust1", since = "1.0.0")]
111 pub use core::slice::{Chunks, Windows};
112 #[stable(feature = "rust1", since = "1.0.0")]
113 pub use core::slice::{Iter, IterMut};
114 #[stable(feature = "rust1", since = "1.0.0")]
115 pub use core::slice::{SplitMut, ChunksMut, Split};
116 #[stable(feature = "rust1", since = "1.0.0")]
117 pub use core::slice::{SplitN, RSplitN, SplitNMut, RSplitNMut};
118 #[unstable(feature = "slice_rsplit", issue = "41020")]
119 pub use core::slice::{RSplit, RSplitMut};
120 #[stable(feature = "rust1", since = "1.0.0")]
121 pub use core::slice::{from_raw_parts, from_raw_parts_mut};
122 #[unstable(feature = "from_ref", issue = "45703")]
123 pub use core::slice::{from_ref, from_ref_mut};
124 #[unstable(feature = "slice_get_slice", issue = "35729")]
125 pub use core::slice::SliceIndex;
127 ////////////////////////////////////////////////////////////////////////////////
128 // Basic slice extension methods
129 ////////////////////////////////////////////////////////////////////////////////
131 // HACK(japaric) needed for the implementation of `vec!` macro during testing
132 // NB see the hack module in this file for more details
134 pub use self::hack::into_vec;
136 // HACK(japaric) needed for the implementation of `Vec::clone` during testing
137 // NB see the hack module in this file for more details
139 pub use self::hack::to_vec;
141 // HACK(japaric): With cfg(test) `impl [T]` is not available, these three
142 // functions are actually methods that are in `impl [T]` but not in
143 // `core::slice::SliceExt` - we need to supply these functions for the
144 // `test_permutations` test
150 use string::ToString;
153 pub fn into_vec<T>(mut b: Box<[T]>) -> Vec<T> {
155 let xs = Vec::from_raw_parts(b.as_mut_ptr(), b.len(), b.len());
162 pub fn to_vec<T>(s: &[T]) -> Vec<T>
165 let mut vector = Vec::with_capacity(s.len());
166 vector.extend_from_slice(s);
174 /// Returns the number of elements in the slice.
179 /// let a = [1, 2, 3];
180 /// assert_eq!(a.len(), 3);
182 #[stable(feature = "rust1", since = "1.0.0")]
184 pub fn len(&self) -> usize {
185 core_slice::SliceExt::len(self)
188 /// Returns `true` if the slice has a length of 0.
193 /// let a = [1, 2, 3];
194 /// assert!(!a.is_empty());
196 #[stable(feature = "rust1", since = "1.0.0")]
198 pub fn is_empty(&self) -> bool {
199 core_slice::SliceExt::is_empty(self)
202 /// Returns the first element of the slice, or `None` if it is empty.
207 /// let v = [10, 40, 30];
208 /// assert_eq!(Some(&10), v.first());
210 /// let w: &[i32] = &[];
211 /// assert_eq!(None, w.first());
213 #[stable(feature = "rust1", since = "1.0.0")]
215 pub fn first(&self) -> Option<&T> {
216 core_slice::SliceExt::first(self)
219 /// Returns a mutable pointer to the first element of the slice, or `None` if it is empty.
224 /// let x = &mut [0, 1, 2];
226 /// if let Some(first) = x.first_mut() {
229 /// assert_eq!(x, &[5, 1, 2]);
231 #[stable(feature = "rust1", since = "1.0.0")]
233 pub fn first_mut(&mut self) -> Option<&mut T> {
234 core_slice::SliceExt::first_mut(self)
237 /// Returns the first and all the rest of the elements of the slice, or `None` if it is empty.
242 /// let x = &[0, 1, 2];
244 /// if let Some((first, elements)) = x.split_first() {
245 /// assert_eq!(first, &0);
246 /// assert_eq!(elements, &[1, 2]);
249 #[stable(feature = "slice_splits", since = "1.5.0")]
251 pub fn split_first(&self) -> Option<(&T, &[T])> {
252 core_slice::SliceExt::split_first(self)
255 /// Returns the first and all the rest of the elements of the slice, or `None` if it is empty.
260 /// let x = &mut [0, 1, 2];
262 /// if let Some((first, elements)) = x.split_first_mut() {
267 /// assert_eq!(x, &[3, 4, 5]);
269 #[stable(feature = "slice_splits", since = "1.5.0")]
271 pub fn split_first_mut(&mut self) -> Option<(&mut T, &mut [T])> {
272 core_slice::SliceExt::split_first_mut(self)
275 /// Returns the last and all the rest of the elements of the slice, or `None` if it is empty.
280 /// let x = &[0, 1, 2];
282 /// if let Some((last, elements)) = x.split_last() {
283 /// assert_eq!(last, &2);
284 /// assert_eq!(elements, &[0, 1]);
287 #[stable(feature = "slice_splits", since = "1.5.0")]
289 pub fn split_last(&self) -> Option<(&T, &[T])> {
290 core_slice::SliceExt::split_last(self)
294 /// Returns the last and all the rest of the elements of the slice, or `None` if it is empty.
299 /// let x = &mut [0, 1, 2];
301 /// if let Some((last, elements)) = x.split_last_mut() {
306 /// assert_eq!(x, &[4, 5, 3]);
308 #[stable(feature = "slice_splits", since = "1.5.0")]
310 pub fn split_last_mut(&mut self) -> Option<(&mut T, &mut [T])> {
311 core_slice::SliceExt::split_last_mut(self)
314 /// Returns the last element of the slice, or `None` if it is empty.
319 /// let v = [10, 40, 30];
320 /// assert_eq!(Some(&30), v.last());
322 /// let w: &[i32] = &[];
323 /// assert_eq!(None, w.last());
325 #[stable(feature = "rust1", since = "1.0.0")]
327 pub fn last(&self) -> Option<&T> {
328 core_slice::SliceExt::last(self)
331 /// Returns a mutable pointer to the last item in the slice.
336 /// let x = &mut [0, 1, 2];
338 /// if let Some(last) = x.last_mut() {
341 /// assert_eq!(x, &[0, 1, 10]);
343 #[stable(feature = "rust1", since = "1.0.0")]
345 pub fn last_mut(&mut self) -> Option<&mut T> {
346 core_slice::SliceExt::last_mut(self)
349 /// Returns a reference to an element or subslice depending on the type of
352 /// - If given a position, returns a reference to the element at that
353 /// position or `None` if out of bounds.
354 /// - If given a range, returns the subslice corresponding to that range,
355 /// or `None` if out of bounds.
360 /// let v = [10, 40, 30];
361 /// assert_eq!(Some(&40), v.get(1));
362 /// assert_eq!(Some(&[10, 40][..]), v.get(0..2));
363 /// assert_eq!(None, v.get(3));
364 /// assert_eq!(None, v.get(0..4));
366 #[stable(feature = "rust1", since = "1.0.0")]
368 pub fn get<I>(&self, index: I) -> Option<&I::Output>
369 where I: SliceIndex<Self>
371 core_slice::SliceExt::get(self, index)
374 /// Returns a mutable reference to an element or subslice depending on the
375 /// type of index (see [`get`]) or `None` if the index is out of bounds.
377 /// [`get`]: #method.get
382 /// let x = &mut [0, 1, 2];
384 /// if let Some(elem) = x.get_mut(1) {
387 /// assert_eq!(x, &[0, 42, 2]);
389 #[stable(feature = "rust1", since = "1.0.0")]
391 pub fn get_mut<I>(&mut self, index: I) -> Option<&mut I::Output>
392 where I: SliceIndex<Self>
394 core_slice::SliceExt::get_mut(self, index)
397 /// Returns a reference to an element or subslice, without doing bounds
400 /// This is generally not recommended, use with caution! For a safe
401 /// alternative see [`get`].
403 /// [`get`]: #method.get
408 /// let x = &[1, 2, 4];
411 /// assert_eq!(x.get_unchecked(1), &2);
414 #[stable(feature = "rust1", since = "1.0.0")]
416 pub unsafe fn get_unchecked<I>(&self, index: I) -> &I::Output
417 where I: SliceIndex<Self>
419 core_slice::SliceExt::get_unchecked(self, index)
422 /// Returns a mutable reference to an element or subslice, without doing
425 /// This is generally not recommended, use with caution! For a safe
426 /// alternative see [`get_mut`].
428 /// [`get_mut`]: #method.get_mut
433 /// let x = &mut [1, 2, 4];
436 /// let elem = x.get_unchecked_mut(1);
439 /// assert_eq!(x, &[1, 13, 4]);
441 #[stable(feature = "rust1", since = "1.0.0")]
443 pub unsafe fn get_unchecked_mut<I>(&mut self, index: I) -> &mut I::Output
444 where I: SliceIndex<Self>
446 core_slice::SliceExt::get_unchecked_mut(self, index)
449 /// Returns a raw pointer to the slice's buffer.
451 /// The caller must ensure that the slice outlives the pointer this
452 /// function returns, or else it will end up pointing to garbage.
454 /// Modifying the container referenced by this slice may cause its buffer
455 /// to be reallocated, which would also make any pointers to it invalid.
460 /// let x = &[1, 2, 4];
461 /// let x_ptr = x.as_ptr();
464 /// for i in 0..x.len() {
465 /// assert_eq!(x.get_unchecked(i), &*x_ptr.offset(i as isize));
469 #[stable(feature = "rust1", since = "1.0.0")]
471 pub fn as_ptr(&self) -> *const T {
472 core_slice::SliceExt::as_ptr(self)
475 /// Returns an unsafe mutable pointer to the slice's buffer.
477 /// The caller must ensure that the slice outlives the pointer this
478 /// function returns, or else it will end up pointing to garbage.
480 /// Modifying the container referenced by this slice may cause its buffer
481 /// to be reallocated, which would also make any pointers to it invalid.
486 /// let x = &mut [1, 2, 4];
487 /// let x_ptr = x.as_mut_ptr();
490 /// for i in 0..x.len() {
491 /// *x_ptr.offset(i as isize) += 2;
494 /// assert_eq!(x, &[3, 4, 6]);
496 #[stable(feature = "rust1", since = "1.0.0")]
498 pub fn as_mut_ptr(&mut self) -> *mut T {
499 core_slice::SliceExt::as_mut_ptr(self)
502 /// Swaps two elements in the slice.
506 /// * a - The index of the first element
507 /// * b - The index of the second element
511 /// Panics if `a` or `b` are out of bounds.
516 /// let mut v = ["a", "b", "c", "d"];
518 /// assert!(v == ["a", "d", "c", "b"]);
520 #[stable(feature = "rust1", since = "1.0.0")]
522 pub fn swap(&mut self, a: usize, b: usize) {
523 core_slice::SliceExt::swap(self, a, b)
526 /// Reverses the order of elements in the slice, in place.
531 /// let mut v = [1, 2, 3];
533 /// assert!(v == [3, 2, 1]);
535 #[stable(feature = "rust1", since = "1.0.0")]
537 pub fn reverse(&mut self) {
538 core_slice::SliceExt::reverse(self)
541 /// Returns an iterator over the slice.
546 /// let x = &[1, 2, 4];
547 /// let mut iterator = x.iter();
549 /// assert_eq!(iterator.next(), Some(&1));
550 /// assert_eq!(iterator.next(), Some(&2));
551 /// assert_eq!(iterator.next(), Some(&4));
552 /// assert_eq!(iterator.next(), None);
554 #[stable(feature = "rust1", since = "1.0.0")]
556 pub fn iter(&self) -> Iter<T> {
557 core_slice::SliceExt::iter(self)
560 /// Returns an iterator that allows modifying each value.
565 /// let x = &mut [1, 2, 4];
566 /// for elem in x.iter_mut() {
569 /// assert_eq!(x, &[3, 4, 6]);
571 #[stable(feature = "rust1", since = "1.0.0")]
573 pub fn iter_mut(&mut self) -> IterMut<T> {
574 core_slice::SliceExt::iter_mut(self)
577 /// Returns an iterator over all contiguous windows of length
578 /// `size`. The windows overlap. If the slice is shorter than
579 /// `size`, the iterator returns no values.
583 /// Panics if `size` is 0.
588 /// let slice = ['r', 'u', 's', 't'];
589 /// let mut iter = slice.windows(2);
590 /// assert_eq!(iter.next().unwrap(), &['r', 'u']);
591 /// assert_eq!(iter.next().unwrap(), &['u', 's']);
592 /// assert_eq!(iter.next().unwrap(), &['s', 't']);
593 /// assert!(iter.next().is_none());
596 /// If the slice is shorter than `size`:
599 /// let slice = ['f', 'o', 'o'];
600 /// let mut iter = slice.windows(4);
601 /// assert!(iter.next().is_none());
603 #[stable(feature = "rust1", since = "1.0.0")]
605 pub fn windows(&self, size: usize) -> Windows<T> {
606 core_slice::SliceExt::windows(self, size)
609 /// Returns an iterator over `size` elements of the slice at a
610 /// time. The chunks are slices and do not overlap. If `size` does
611 /// not divide the length of the slice, then the last chunk will
612 /// not have length `size`.
616 /// Panics if `size` is 0.
621 /// let slice = ['l', 'o', 'r', 'e', 'm'];
622 /// let mut iter = slice.chunks(2);
623 /// assert_eq!(iter.next().unwrap(), &['l', 'o']);
624 /// assert_eq!(iter.next().unwrap(), &['r', 'e']);
625 /// assert_eq!(iter.next().unwrap(), &['m']);
626 /// assert!(iter.next().is_none());
628 #[stable(feature = "rust1", since = "1.0.0")]
630 pub fn chunks(&self, size: usize) -> Chunks<T> {
631 core_slice::SliceExt::chunks(self, size)
634 /// Returns an iterator over `chunk_size` elements of the slice at a time.
635 /// The chunks are mutable slices, and do not overlap. If `chunk_size` does
636 /// not divide the length of the slice, then the last chunk will not
637 /// have length `chunk_size`.
641 /// Panics if `chunk_size` is 0.
646 /// let v = &mut [0, 0, 0, 0, 0];
647 /// let mut count = 1;
649 /// for chunk in v.chunks_mut(2) {
650 /// for elem in chunk.iter_mut() {
655 /// assert_eq!(v, &[1, 1, 2, 2, 3]);
657 #[stable(feature = "rust1", since = "1.0.0")]
659 pub fn chunks_mut(&mut self, chunk_size: usize) -> ChunksMut<T> {
660 core_slice::SliceExt::chunks_mut(self, chunk_size)
663 /// Divides one slice into two at an index.
665 /// The first will contain all indices from `[0, mid)` (excluding
666 /// the index `mid` itself) and the second will contain all
667 /// indices from `[mid, len)` (excluding the index `len` itself).
671 /// Panics if `mid > len`.
676 /// let v = [1, 2, 3, 4, 5, 6];
679 /// let (left, right) = v.split_at(0);
680 /// assert!(left == []);
681 /// assert!(right == [1, 2, 3, 4, 5, 6]);
685 /// let (left, right) = v.split_at(2);
686 /// assert!(left == [1, 2]);
687 /// assert!(right == [3, 4, 5, 6]);
691 /// let (left, right) = v.split_at(6);
692 /// assert!(left == [1, 2, 3, 4, 5, 6]);
693 /// assert!(right == []);
696 #[stable(feature = "rust1", since = "1.0.0")]
698 pub fn split_at(&self, mid: usize) -> (&[T], &[T]) {
699 core_slice::SliceExt::split_at(self, mid)
702 /// Divides one `&mut` into two at an index.
704 /// The first will contain all indices from `[0, mid)` (excluding
705 /// the index `mid` itself) and the second will contain all
706 /// indices from `[mid, len)` (excluding the index `len` itself).
710 /// Panics if `mid > len`.
715 /// let mut v = [1, 0, 3, 0, 5, 6];
716 /// // scoped to restrict the lifetime of the borrows
718 /// let (left, right) = v.split_at_mut(2);
719 /// assert!(left == [1, 0]);
720 /// assert!(right == [3, 0, 5, 6]);
724 /// assert!(v == [1, 2, 3, 4, 5, 6]);
726 #[stable(feature = "rust1", since = "1.0.0")]
728 pub fn split_at_mut(&mut self, mid: usize) -> (&mut [T], &mut [T]) {
729 core_slice::SliceExt::split_at_mut(self, mid)
732 /// Returns an iterator over subslices separated by elements that match
733 /// `pred`. The matched element is not contained in the subslices.
738 /// let slice = [10, 40, 33, 20];
739 /// let mut iter = slice.split(|num| num % 3 == 0);
741 /// assert_eq!(iter.next().unwrap(), &[10, 40]);
742 /// assert_eq!(iter.next().unwrap(), &[20]);
743 /// assert!(iter.next().is_none());
746 /// If the first element is matched, an empty slice will be the first item
747 /// returned by the iterator. Similarly, if the last element in the slice
748 /// is matched, an empty slice will be the last item returned by the
752 /// let slice = [10, 40, 33];
753 /// let mut iter = slice.split(|num| num % 3 == 0);
755 /// assert_eq!(iter.next().unwrap(), &[10, 40]);
756 /// assert_eq!(iter.next().unwrap(), &[]);
757 /// assert!(iter.next().is_none());
760 /// If two matched elements are directly adjacent, an empty slice will be
761 /// present between them:
764 /// let slice = [10, 6, 33, 20];
765 /// let mut iter = slice.split(|num| num % 3 == 0);
767 /// assert_eq!(iter.next().unwrap(), &[10]);
768 /// assert_eq!(iter.next().unwrap(), &[]);
769 /// assert_eq!(iter.next().unwrap(), &[20]);
770 /// assert!(iter.next().is_none());
772 #[stable(feature = "rust1", since = "1.0.0")]
774 pub fn split<F>(&self, pred: F) -> Split<T, F>
775 where F: FnMut(&T) -> bool
777 core_slice::SliceExt::split(self, pred)
780 /// Returns an iterator over mutable subslices separated by elements that
781 /// match `pred`. The matched element is not contained in the subslices.
786 /// let mut v = [10, 40, 30, 20, 60, 50];
788 /// for group in v.split_mut(|num| *num % 3 == 0) {
791 /// assert_eq!(v, [1, 40, 30, 1, 60, 1]);
793 #[stable(feature = "rust1", since = "1.0.0")]
795 pub fn split_mut<F>(&mut self, pred: F) -> SplitMut<T, F>
796 where F: FnMut(&T) -> bool
798 core_slice::SliceExt::split_mut(self, pred)
801 /// Returns an iterator over subslices separated by elements that match
802 /// `pred`, starting at the end of the slice and working backwards.
803 /// The matched element is not contained in the subslices.
808 /// #![feature(slice_rsplit)]
810 /// let slice = [11, 22, 33, 0, 44, 55];
811 /// let mut iter = slice.rsplit(|num| *num == 0);
813 /// assert_eq!(iter.next().unwrap(), &[44, 55]);
814 /// assert_eq!(iter.next().unwrap(), &[11, 22, 33]);
815 /// assert_eq!(iter.next(), None);
818 /// As with `split()`, if the first or last element is matched, an empty
819 /// slice will be the first (or last) item returned by the iterator.
822 /// #![feature(slice_rsplit)]
824 /// let v = &[0, 1, 1, 2, 3, 5, 8];
825 /// let mut it = v.rsplit(|n| *n % 2 == 0);
826 /// assert_eq!(it.next().unwrap(), &[]);
827 /// assert_eq!(it.next().unwrap(), &[3, 5]);
828 /// assert_eq!(it.next().unwrap(), &[1, 1]);
829 /// assert_eq!(it.next().unwrap(), &[]);
830 /// assert_eq!(it.next(), None);
832 #[unstable(feature = "slice_rsplit", issue = "41020")]
834 pub fn rsplit<F>(&self, pred: F) -> RSplit<T, F>
835 where F: FnMut(&T) -> bool
837 core_slice::SliceExt::rsplit(self, pred)
840 /// Returns an iterator over mutable subslices separated by elements that
841 /// match `pred`, starting at the end of the slice and working
842 /// backwards. The matched element is not contained in the subslices.
847 /// #![feature(slice_rsplit)]
849 /// let mut v = [100, 400, 300, 200, 600, 500];
851 /// let mut count = 0;
852 /// for group in v.rsplit_mut(|num| *num % 3 == 0) {
854 /// group[0] = count;
856 /// assert_eq!(v, [3, 400, 300, 2, 600, 1]);
859 #[unstable(feature = "slice_rsplit", issue = "41020")]
861 pub fn rsplit_mut<F>(&mut self, pred: F) -> RSplitMut<T, F>
862 where F: FnMut(&T) -> bool
864 core_slice::SliceExt::rsplit_mut(self, pred)
867 /// Returns an iterator over subslices separated by elements that match
868 /// `pred`, limited to returning at most `n` items. The matched element is
869 /// not contained in the subslices.
871 /// The last element returned, if any, will contain the remainder of the
876 /// Print the slice split once by numbers divisible by 3 (i.e. `[10, 40]`,
880 /// let v = [10, 40, 30, 20, 60, 50];
882 /// for group in v.splitn(2, |num| *num % 3 == 0) {
883 /// println!("{:?}", group);
886 #[stable(feature = "rust1", since = "1.0.0")]
888 pub fn splitn<F>(&self, n: usize, pred: F) -> SplitN<T, F>
889 where F: FnMut(&T) -> bool
891 core_slice::SliceExt::splitn(self, n, pred)
894 /// Returns an iterator over subslices separated by elements that match
895 /// `pred`, limited to returning at most `n` items. The matched element is
896 /// not contained in the subslices.
898 /// The last element returned, if any, will contain the remainder of the
904 /// let mut v = [10, 40, 30, 20, 60, 50];
906 /// for group in v.splitn_mut(2, |num| *num % 3 == 0) {
909 /// assert_eq!(v, [1, 40, 30, 1, 60, 50]);
911 #[stable(feature = "rust1", since = "1.0.0")]
913 pub fn splitn_mut<F>(&mut self, n: usize, pred: F) -> SplitNMut<T, F>
914 where F: FnMut(&T) -> bool
916 core_slice::SliceExt::splitn_mut(self, n, pred)
919 /// Returns an iterator over subslices separated by elements that match
920 /// `pred` limited to returning at most `n` items. This starts at the end of
921 /// the slice and works backwards. The matched element is not contained in
924 /// The last element returned, if any, will contain the remainder of the
929 /// Print the slice split once, starting from the end, by numbers divisible
930 /// by 3 (i.e. `[50]`, `[10, 40, 30, 20]`):
933 /// let v = [10, 40, 30, 20, 60, 50];
935 /// for group in v.rsplitn(2, |num| *num % 3 == 0) {
936 /// println!("{:?}", group);
939 #[stable(feature = "rust1", since = "1.0.0")]
941 pub fn rsplitn<F>(&self, n: usize, pred: F) -> RSplitN<T, F>
942 where F: FnMut(&T) -> bool
944 core_slice::SliceExt::rsplitn(self, n, pred)
947 /// Returns an iterator over subslices separated by elements that match
948 /// `pred` limited to returning at most `n` items. This starts at the end of
949 /// the slice and works backwards. The matched element is not contained in
952 /// The last element returned, if any, will contain the remainder of the
958 /// let mut s = [10, 40, 30, 20, 60, 50];
960 /// for group in s.rsplitn_mut(2, |num| *num % 3 == 0) {
963 /// assert_eq!(s, [1, 40, 30, 20, 60, 1]);
965 #[stable(feature = "rust1", since = "1.0.0")]
967 pub fn rsplitn_mut<F>(&mut self, n: usize, pred: F) -> RSplitNMut<T, F>
968 where F: FnMut(&T) -> bool
970 core_slice::SliceExt::rsplitn_mut(self, n, pred)
973 /// Returns `true` if the slice contains an element with the given value.
978 /// let v = [10, 40, 30];
979 /// assert!(v.contains(&30));
980 /// assert!(!v.contains(&50));
982 #[stable(feature = "rust1", since = "1.0.0")]
983 pub fn contains(&self, x: &T) -> bool
986 core_slice::SliceExt::contains(self, x)
989 /// Returns `true` if `needle` is a prefix of the slice.
994 /// let v = [10, 40, 30];
995 /// assert!(v.starts_with(&[10]));
996 /// assert!(v.starts_with(&[10, 40]));
997 /// assert!(!v.starts_with(&[50]));
998 /// assert!(!v.starts_with(&[10, 50]));
1001 /// Always returns `true` if `needle` is an empty slice:
1004 /// let v = &[10, 40, 30];
1005 /// assert!(v.starts_with(&[]));
1006 /// let v: &[u8] = &[];
1007 /// assert!(v.starts_with(&[]));
1009 #[stable(feature = "rust1", since = "1.0.0")]
1010 pub fn starts_with(&self, needle: &[T]) -> bool
1013 core_slice::SliceExt::starts_with(self, needle)
1016 /// Returns `true` if `needle` is a suffix of the slice.
1021 /// let v = [10, 40, 30];
1022 /// assert!(v.ends_with(&[30]));
1023 /// assert!(v.ends_with(&[40, 30]));
1024 /// assert!(!v.ends_with(&[50]));
1025 /// assert!(!v.ends_with(&[50, 30]));
1028 /// Always returns `true` if `needle` is an empty slice:
1031 /// let v = &[10, 40, 30];
1032 /// assert!(v.ends_with(&[]));
1033 /// let v: &[u8] = &[];
1034 /// assert!(v.ends_with(&[]));
1036 #[stable(feature = "rust1", since = "1.0.0")]
1037 pub fn ends_with(&self, needle: &[T]) -> bool
1040 core_slice::SliceExt::ends_with(self, needle)
1043 /// Binary searches this sorted slice for a given element.
1045 /// If the value is found then `Ok` is returned, containing the
1046 /// index of the matching element; if the value is not found then
1047 /// `Err` is returned, containing the index where a matching
1048 /// element could be inserted while maintaining sorted order.
1052 /// Looks up a series of four elements. The first is found, with a
1053 /// uniquely determined position; the second and third are not
1054 /// found; the fourth could match any position in `[1, 4]`.
1057 /// let s = [0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55];
1059 /// assert_eq!(s.binary_search(&13), Ok(9));
1060 /// assert_eq!(s.binary_search(&4), Err(7));
1061 /// assert_eq!(s.binary_search(&100), Err(13));
1062 /// let r = s.binary_search(&1);
1063 /// assert!(match r { Ok(1...4) => true, _ => false, });
1065 #[stable(feature = "rust1", since = "1.0.0")]
1066 pub fn binary_search(&self, x: &T) -> Result<usize, usize>
1069 core_slice::SliceExt::binary_search(self, x)
1072 /// Binary searches this sorted slice with a comparator function.
1074 /// The comparator function should implement an order consistent
1075 /// with the sort order of the underlying slice, returning an
1076 /// order code that indicates whether its argument is `Less`,
1077 /// `Equal` or `Greater` the desired target.
1079 /// If a matching value is found then returns `Ok`, containing
1080 /// the index for the matched element; if no match is found then
1081 /// `Err` is returned, containing the index where a matching
1082 /// element could be inserted while maintaining sorted order.
1086 /// Looks up a series of four elements. The first is found, with a
1087 /// uniquely determined position; the second and third are not
1088 /// found; the fourth could match any position in `[1, 4]`.
1091 /// let s = [0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55];
1094 /// assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Ok(9));
1096 /// assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Err(7));
1098 /// assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Err(13));
1100 /// let r = s.binary_search_by(|probe| probe.cmp(&seek));
1101 /// assert!(match r { Ok(1...4) => true, _ => false, });
1103 #[stable(feature = "rust1", since = "1.0.0")]
1105 pub fn binary_search_by<'a, F>(&'a self, f: F) -> Result<usize, usize>
1106 where F: FnMut(&'a T) -> Ordering
1108 core_slice::SliceExt::binary_search_by(self, f)
1111 /// Binary searches this sorted slice with a key extraction function.
1113 /// Assumes that the slice is sorted by the key, for instance with
1114 /// [`sort_by_key`] using the same key extraction function.
1116 /// If a matching value is found then returns `Ok`, containing the
1117 /// index for the matched element; if no match is found then `Err`
1118 /// is returned, containing the index where a matching element could
1119 /// be inserted while maintaining sorted order.
1121 /// [`sort_by_key`]: #method.sort_by_key
1125 /// Looks up a series of four elements in a slice of pairs sorted by
1126 /// their second elements. The first is found, with a uniquely
1127 /// determined position; the second and third are not found; the
1128 /// fourth could match any position in `[1, 4]`.
1131 /// let s = [(0, 0), (2, 1), (4, 1), (5, 1), (3, 1),
1132 /// (1, 2), (2, 3), (4, 5), (5, 8), (3, 13),
1133 /// (1, 21), (2, 34), (4, 55)];
1135 /// assert_eq!(s.binary_search_by_key(&13, |&(a,b)| b), Ok(9));
1136 /// assert_eq!(s.binary_search_by_key(&4, |&(a,b)| b), Err(7));
1137 /// assert_eq!(s.binary_search_by_key(&100, |&(a,b)| b), Err(13));
1138 /// let r = s.binary_search_by_key(&1, |&(a,b)| b);
1139 /// assert!(match r { Ok(1...4) => true, _ => false, });
1141 #[stable(feature = "slice_binary_search_by_key", since = "1.10.0")]
1143 pub fn binary_search_by_key<'a, B, F>(&'a self, b: &B, f: F) -> Result<usize, usize>
1144 where F: FnMut(&'a T) -> B,
1147 core_slice::SliceExt::binary_search_by_key(self, b, f)
1150 /// Sorts the slice.
1152 /// This sort is stable (i.e. does not reorder equal elements) and `O(n log n)` worst-case.
1154 /// When applicable, unstable sorting is preferred because it is generally faster than stable
1155 /// sorting and it doesn't allocate auxiliary memory.
1156 /// See [`sort_unstable`](#method.sort_unstable).
1158 /// # Current implementation
1160 /// The current algorithm is an adaptive, iterative merge sort inspired by
1161 /// [timsort](https://en.wikipedia.org/wiki/Timsort).
1162 /// It is designed to be very fast in cases where the slice is nearly sorted, or consists of
1163 /// two or more sorted sequences concatenated one after another.
1165 /// Also, it allocates temporary storage half the size of `self`, but for short slices a
1166 /// non-allocating insertion sort is used instead.
1171 /// let mut v = [-5, 4, 1, -3, 2];
1174 /// assert!(v == [-5, -3, 1, 2, 4]);
1176 #[stable(feature = "rust1", since = "1.0.0")]
1178 pub fn sort(&mut self)
1181 merge_sort(self, |a, b| a.lt(b));
1184 /// Sorts the slice with a comparator function.
1186 /// This sort is stable (i.e. does not reorder equal elements) and `O(n log n)` worst-case.
1188 /// When applicable, unstable sorting is preferred because it is generally faster than stable
1189 /// sorting and it doesn't allocate auxiliary memory.
1190 /// See [`sort_unstable_by`](#method.sort_unstable_by).
1192 /// # Current implementation
1194 /// The current algorithm is an adaptive, iterative merge sort inspired by
1195 /// [timsort](https://en.wikipedia.org/wiki/Timsort).
1196 /// It is designed to be very fast in cases where the slice is nearly sorted, or consists of
1197 /// two or more sorted sequences concatenated one after another.
1199 /// Also, it allocates temporary storage half the size of `self`, but for short slices a
1200 /// non-allocating insertion sort is used instead.
1205 /// let mut v = [5, 4, 1, 3, 2];
1206 /// v.sort_by(|a, b| a.cmp(b));
1207 /// assert!(v == [1, 2, 3, 4, 5]);
1209 /// // reverse sorting
1210 /// v.sort_by(|a, b| b.cmp(a));
1211 /// assert!(v == [5, 4, 3, 2, 1]);
1213 #[stable(feature = "rust1", since = "1.0.0")]
1215 pub fn sort_by<F>(&mut self, mut compare: F)
1216 where F: FnMut(&T, &T) -> Ordering
1218 merge_sort(self, |a, b| compare(a, b) == Less);
1221 /// Sorts the slice with a key extraction function.
1223 /// This sort is stable (i.e. does not reorder equal elements) and `O(n log n)` worst-case.
1225 /// When applicable, unstable sorting is preferred because it is generally faster than stable
1226 /// sorting and it doesn't allocate auxiliary memory.
1227 /// See [`sort_unstable_by_key`](#method.sort_unstable_by_key).
1229 /// # Current implementation
1231 /// The current algorithm is an adaptive, iterative merge sort inspired by
1232 /// [timsort](https://en.wikipedia.org/wiki/Timsort).
1233 /// It is designed to be very fast in cases where the slice is nearly sorted, or consists of
1234 /// two or more sorted sequences concatenated one after another.
1236 /// Also, it allocates temporary storage half the size of `self`, but for short slices a
1237 /// non-allocating insertion sort is used instead.
1242 /// let mut v = [-5i32, 4, 1, -3, 2];
1244 /// v.sort_by_key(|k| k.abs());
1245 /// assert!(v == [1, 2, -3, 4, -5]);
1247 #[stable(feature = "slice_sort_by_key", since = "1.7.0")]
1249 pub fn sort_by_key<B, F>(&mut self, mut f: F)
1250 where F: FnMut(&T) -> B, B: Ord
1252 merge_sort(self, |a, b| f(a).lt(&f(b)));
1255 /// Sorts the slice, but may not preserve the order of equal elements.
1257 /// This sort is unstable (i.e. may reorder equal elements), in-place (i.e. does not allocate),
1258 /// and `O(n log n)` worst-case.
1260 /// # Current implementation
1262 /// The current algorithm is based on [pattern-defeating quicksort][pdqsort] by Orson Peters,
1263 /// which combines the fast average case of randomized quicksort with the fast worst case of
1264 /// heapsort, while achieving linear time on slices with certain patterns. It uses some
1265 /// randomization to avoid degenerate cases, but with a fixed seed to always provide
1266 /// deterministic behavior.
1268 /// It is typically faster than stable sorting, except in a few special cases, e.g. when the
1269 /// slice consists of several concatenated sorted sequences.
1274 /// let mut v = [-5, 4, 1, -3, 2];
1276 /// v.sort_unstable();
1277 /// assert!(v == [-5, -3, 1, 2, 4]);
1280 /// [pdqsort]: https://github.com/orlp/pdqsort
1281 #[stable(feature = "sort_unstable", since = "1.20.0")]
1283 pub fn sort_unstable(&mut self)
1286 core_slice::SliceExt::sort_unstable(self);
1289 /// Sorts the slice with a comparator function, but may not preserve the order of equal
1292 /// This sort is unstable (i.e. may reorder equal elements), in-place (i.e. does not allocate),
1293 /// and `O(n log n)` worst-case.
1295 /// # Current implementation
1297 /// The current algorithm is based on [pattern-defeating quicksort][pdqsort] by Orson Peters,
1298 /// which combines the fast average case of randomized quicksort with the fast worst case of
1299 /// heapsort, while achieving linear time on slices with certain patterns. It uses some
1300 /// randomization to avoid degenerate cases, but with a fixed seed to always provide
1301 /// deterministic behavior.
1303 /// It is typically faster than stable sorting, except in a few special cases, e.g. when the
1304 /// slice consists of several concatenated sorted sequences.
1309 /// let mut v = [5, 4, 1, 3, 2];
1310 /// v.sort_unstable_by(|a, b| a.cmp(b));
1311 /// assert!(v == [1, 2, 3, 4, 5]);
1313 /// // reverse sorting
1314 /// v.sort_unstable_by(|a, b| b.cmp(a));
1315 /// assert!(v == [5, 4, 3, 2, 1]);
1318 /// [pdqsort]: https://github.com/orlp/pdqsort
1319 #[stable(feature = "sort_unstable", since = "1.20.0")]
1321 pub fn sort_unstable_by<F>(&mut self, compare: F)
1322 where F: FnMut(&T, &T) -> Ordering
1324 core_slice::SliceExt::sort_unstable_by(self, compare);
1327 /// Sorts the slice with a key extraction function, but may not preserve the order of equal
1330 /// This sort is unstable (i.e. may reorder equal elements), in-place (i.e. does not allocate),
1331 /// and `O(n log n)` worst-case.
1333 /// # Current implementation
1335 /// The current algorithm is based on [pattern-defeating quicksort][pdqsort] by Orson Peters,
1336 /// which combines the fast average case of randomized quicksort with the fast worst case of
1337 /// heapsort, while achieving linear time on slices with certain patterns. It uses some
1338 /// randomization to avoid degenerate cases, but with a fixed seed to always provide
1339 /// deterministic behavior.
1341 /// It is typically faster than stable sorting, except in a few special cases, e.g. when the
1342 /// slice consists of several concatenated sorted sequences.
1347 /// let mut v = [-5i32, 4, 1, -3, 2];
1349 /// v.sort_unstable_by_key(|k| k.abs());
1350 /// assert!(v == [1, 2, -3, 4, -5]);
1353 /// [pdqsort]: https://github.com/orlp/pdqsort
1354 #[stable(feature = "sort_unstable", since = "1.20.0")]
1356 pub fn sort_unstable_by_key<B, F>(&mut self, f: F)
1357 where F: FnMut(&T) -> B,
1360 core_slice::SliceExt::sort_unstable_by_key(self, f);
1363 /// Permutes the slice in-place such that `self[mid..]` moves to the
1364 /// beginning of the slice while `self[..mid]` moves to the end of the
1365 /// slice. Equivalently, rotates the slice `mid` places to the left
1366 /// or `k = self.len() - mid` places to the right.
1368 /// This is a "k-rotation", a permutation in which item `i` moves to
1369 /// position `i + k`, modulo the length of the slice. See _Elements
1370 /// of Programming_ [§10.4][eop].
1372 /// Rotation by `mid` and rotation by `k` are inverse operations.
1374 /// [eop]: https://books.google.com/books?id=CO9ULZGINlsC&pg=PA178&q=k-rotation
1378 /// This function will panic if `mid` is greater than the length of the
1379 /// slice. (Note that `mid == self.len()` does _not_ panic; it's a nop
1380 /// rotation with `k == 0`, the inverse of a rotation with `mid == 0`.)
1384 /// Takes linear (in `self.len()`) time.
1389 /// #![feature(slice_rotate)]
1391 /// let mut a = [1, 2, 3, 4, 5, 6, 7];
1394 /// assert_eq!(&a, &[3, 4, 5, 6, 7, 1, 2]);
1395 /// let k = a.len() - mid;
1397 /// assert_eq!(&a, &[1, 2, 3, 4, 5, 6, 7]);
1399 /// use std::ops::Range;
1400 /// fn slide<T>(slice: &mut [T], range: Range<usize>, to: usize) {
1401 /// if to < range.start {
1402 /// slice[to..range.end].rotate(range.start-to);
1403 /// } else if to > range.end {
1404 /// slice[range.start..to].rotate(range.end-range.start);
1407 /// let mut v: Vec<_> = (0..10).collect();
1408 /// slide(&mut v, 1..4, 7);
1409 /// assert_eq!(&v, &[0, 4, 5, 6, 1, 2, 3, 7, 8, 9]);
1410 /// slide(&mut v, 6..8, 1);
1411 /// assert_eq!(&v, &[0, 3, 7, 4, 5, 6, 1, 2, 8, 9]);
1413 #[unstable(feature = "slice_rotate", issue = "41891")]
1414 pub fn rotate(&mut self, mid: usize) {
1415 core_slice::SliceExt::rotate(self, mid);
1418 /// Copies the elements from `src` into `self`.
1420 /// The length of `src` must be the same as `self`.
1422 /// If `src` implements `Copy`, it can be more performant to use
1423 /// [`copy_from_slice`].
1427 /// This function will panic if the two slices have different lengths.
1432 /// let mut dst = [0, 0, 0];
1433 /// let src = [1, 2, 3];
1435 /// dst.clone_from_slice(&src);
1436 /// assert!(dst == [1, 2, 3]);
1439 /// [`copy_from_slice`]: #method.copy_from_slice
1440 #[stable(feature = "clone_from_slice", since = "1.7.0")]
1441 pub fn clone_from_slice(&mut self, src: &[T]) where T: Clone {
1442 core_slice::SliceExt::clone_from_slice(self, src)
1445 /// Copies all elements from `src` into `self`, using a memcpy.
1447 /// The length of `src` must be the same as `self`.
1449 /// If `src` does not implement `Copy`, use [`clone_from_slice`].
1453 /// This function will panic if the two slices have different lengths.
1458 /// let mut dst = [0, 0, 0];
1459 /// let src = [1, 2, 3];
1461 /// dst.copy_from_slice(&src);
1462 /// assert_eq!(src, dst);
1465 /// [`clone_from_slice`]: #method.clone_from_slice
1466 #[stable(feature = "copy_from_slice", since = "1.9.0")]
1467 pub fn copy_from_slice(&mut self, src: &[T]) where T: Copy {
1468 core_slice::SliceExt::copy_from_slice(self, src)
1471 /// Swaps all elements in `self` with those in `src`.
1473 /// The length of `src` must be the same as `self`.
1477 /// This function will panic if the two slices have different lengths.
1482 /// #![feature(swap_with_slice)]
1484 /// let mut src = [1, 2, 3];
1485 /// let mut dst = [7, 8, 9];
1487 /// src.swap_with_slice(&mut dst);
1488 /// assert_eq!(src, [7, 8, 9]);
1489 /// assert_eq!(dst, [1, 2, 3]);
1491 #[unstable(feature = "swap_with_slice", issue = "44030")]
1492 pub fn swap_with_slice(&mut self, src: &mut [T]) {
1493 core_slice::SliceExt::swap_with_slice(self, src)
1496 /// Copies `self` into a new `Vec`.
1501 /// let s = [10, 40, 30];
1502 /// let x = s.to_vec();
1503 /// // Here, `s` and `x` can be modified independently.
1505 #[stable(feature = "rust1", since = "1.0.0")]
1507 pub fn to_vec(&self) -> Vec<T>
1510 // NB see hack module in this file
1514 /// Converts `self` into a vector without clones or allocation.
1516 /// The resulting vector can be converted back into a box via
1517 /// `Vec<T>`'s `into_boxed_slice` method.
1522 /// let s: Box<[i32]> = Box::new([10, 40, 30]);
1523 /// let x = s.into_vec();
1524 /// // `s` cannot be used anymore because it has been converted into `x`.
1526 /// assert_eq!(x, vec![10, 40, 30]);
1528 #[stable(feature = "rust1", since = "1.0.0")]
1530 pub fn into_vec(self: Box<Self>) -> Vec<T> {
1531 // NB see hack module in this file
1532 hack::into_vec(self)
1536 ////////////////////////////////////////////////////////////////////////////////
1537 // Extension traits for slices over specific kinds of data
1538 ////////////////////////////////////////////////////////////////////////////////
1539 #[unstable(feature = "slice_concat_ext",
1540 reason = "trait should not have to exist",
1542 /// An extension trait for concatenating slices
1543 pub trait SliceConcatExt<T: ?Sized> {
1544 #[unstable(feature = "slice_concat_ext",
1545 reason = "trait should not have to exist",
1547 /// The resulting type after concatenation
1550 /// Flattens a slice of `T` into a single value `Self::Output`.
1555 /// assert_eq!(["hello", "world"].concat(), "helloworld");
1556 /// assert_eq!([[1, 2], [3, 4]].concat(), [1, 2, 3, 4]);
1558 #[stable(feature = "rust1", since = "1.0.0")]
1559 fn concat(&self) -> Self::Output;
1561 /// Flattens a slice of `T` into a single value `Self::Output`, placing a
1562 /// given separator between each.
1567 /// assert_eq!(["hello", "world"].join(" "), "hello world");
1568 /// assert_eq!([[1, 2], [3, 4]].join(&0), [1, 2, 0, 3, 4]);
1570 #[stable(feature = "rename_connect_to_join", since = "1.3.0")]
1571 fn join(&self, sep: &T) -> Self::Output;
1573 #[stable(feature = "rust1", since = "1.0.0")]
1574 #[rustc_deprecated(since = "1.3.0", reason = "renamed to join")]
1575 fn connect(&self, sep: &T) -> Self::Output;
1578 #[unstable(feature = "slice_concat_ext",
1579 reason = "trait should not have to exist",
1581 impl<T: Clone, V: Borrow<[T]>> SliceConcatExt<T> for [V] {
1582 type Output = Vec<T>;
1584 fn concat(&self) -> Vec<T> {
1585 let size = self.iter().fold(0, |acc, v| acc + v.borrow().len());
1586 let mut result = Vec::with_capacity(size);
1588 result.extend_from_slice(v.borrow())
1593 fn join(&self, sep: &T) -> Vec<T> {
1594 let size = self.iter().fold(0, |acc, v| acc + v.borrow().len());
1595 let mut result = Vec::with_capacity(size + self.len());
1596 let mut first = true;
1601 result.push(sep.clone())
1603 result.extend_from_slice(v.borrow())
1608 fn connect(&self, sep: &T) -> Vec<T> {
1613 ////////////////////////////////////////////////////////////////////////////////
1614 // Standard trait implementations for slices
1615 ////////////////////////////////////////////////////////////////////////////////
1617 #[stable(feature = "rust1", since = "1.0.0")]
1618 impl<T> Borrow<[T]> for Vec<T> {
1619 fn borrow(&self) -> &[T] {
1624 #[stable(feature = "rust1", since = "1.0.0")]
1625 impl<T> BorrowMut<[T]> for Vec<T> {
1626 fn borrow_mut(&mut self) -> &mut [T] {
1631 #[stable(feature = "rust1", since = "1.0.0")]
1632 impl<T: Clone> ToOwned for [T] {
1633 type Owned = Vec<T>;
1635 fn to_owned(&self) -> Vec<T> {
1640 fn to_owned(&self) -> Vec<T> {
1644 fn clone_into(&self, target: &mut Vec<T>) {
1645 // drop anything in target that will not be overwritten
1646 target.truncate(self.len());
1647 let len = target.len();
1649 // reuse the contained values' allocations/resources.
1650 target.clone_from_slice(&self[..len]);
1652 // target.len <= self.len due to the truncate above, so the
1653 // slice here is always in-bounds.
1654 target.extend_from_slice(&self[len..]);
1658 ////////////////////////////////////////////////////////////////////////////////
1660 ////////////////////////////////////////////////////////////////////////////////
1662 /// Inserts `v[0]` into pre-sorted sequence `v[1..]` so that whole `v[..]` becomes sorted.
1664 /// This is the integral subroutine of insertion sort.
1665 fn insert_head<T, F>(v: &mut [T], is_less: &mut F)
1666 where F: FnMut(&T, &T) -> bool
1668 if v.len() >= 2 && is_less(&v[1], &v[0]) {
1670 // There are three ways to implement insertion here:
1672 // 1. Swap adjacent elements until the first one gets to its final destination.
1673 // However, this way we copy data around more than is necessary. If elements are big
1674 // structures (costly to copy), this method will be slow.
1676 // 2. Iterate until the right place for the first element is found. Then shift the
1677 // elements succeeding it to make room for it and finally place it into the
1678 // remaining hole. This is a good method.
1680 // 3. Copy the first element into a temporary variable. Iterate until the right place
1681 // for it is found. As we go along, copy every traversed element into the slot
1682 // preceding it. Finally, copy data from the temporary variable into the remaining
1683 // hole. This method is very good. Benchmarks demonstrated slightly better
1684 // performance than with the 2nd method.
1686 // All methods were benchmarked, and the 3rd showed best results. So we chose that one.
1687 let mut tmp = mem::ManuallyDrop::new(ptr::read(&v[0]));
1689 // Intermediate state of the insertion process is always tracked by `hole`, which
1690 // serves two purposes:
1691 // 1. Protects integrity of `v` from panics in `is_less`.
1692 // 2. Fills the remaining hole in `v` in the end.
1696 // If `is_less` panics at any point during the process, `hole` will get dropped and
1697 // fill the hole in `v` with `tmp`, thus ensuring that `v` still holds every object it
1698 // initially held exactly once.
1699 let mut hole = InsertionHole {
1703 ptr::copy_nonoverlapping(&v[1], &mut v[0], 1);
1705 for i in 2..v.len() {
1706 if !is_less(&v[i], &*tmp) {
1709 ptr::copy_nonoverlapping(&v[i], &mut v[i - 1], 1);
1710 hole.dest = &mut v[i];
1712 // `hole` gets dropped and thus copies `tmp` into the remaining hole in `v`.
1716 // When dropped, copies from `src` into `dest`.
1717 struct InsertionHole<T> {
1722 impl<T> Drop for InsertionHole<T> {
1723 fn drop(&mut self) {
1724 unsafe { ptr::copy_nonoverlapping(self.src, self.dest, 1); }
1729 /// Merges non-decreasing runs `v[..mid]` and `v[mid..]` using `buf` as temporary storage, and
1730 /// stores the result into `v[..]`.
1734 /// The two slices must be non-empty and `mid` must be in bounds. Buffer `buf` must be long enough
1735 /// to hold a copy of the shorter slice. Also, `T` must not be a zero-sized type.
1736 unsafe fn merge<T, F>(v: &mut [T], mid: usize, buf: *mut T, is_less: &mut F)
1737 where F: FnMut(&T, &T) -> bool
1740 let v = v.as_mut_ptr();
1741 let v_mid = v.offset(mid as isize);
1742 let v_end = v.offset(len as isize);
1744 // The merge process first copies the shorter run into `buf`. Then it traces the newly copied
1745 // run and the longer run forwards (or backwards), comparing their next unconsumed elements and
1746 // copying the lesser (or greater) one into `v`.
1748 // As soon as the shorter run is fully consumed, the process is done. If the longer run gets
1749 // consumed first, then we must copy whatever is left of the shorter run into the remaining
1752 // Intermediate state of the process is always tracked by `hole`, which serves two purposes:
1753 // 1. Protects integrity of `v` from panics in `is_less`.
1754 // 2. Fills the remaining hole in `v` if the longer run gets consumed first.
1758 // If `is_less` panics at any point during the process, `hole` will get dropped and fill the
1759 // hole in `v` with the unconsumed range in `buf`, thus ensuring that `v` still holds every
1760 // object it initially held exactly once.
1763 if mid <= len - mid {
1764 // The left run is shorter.
1765 ptr::copy_nonoverlapping(v, buf, mid);
1768 end: buf.offset(mid as isize),
1772 // Initially, these pointers point to the beginnings of their arrays.
1773 let left = &mut hole.start;
1774 let mut right = v_mid;
1775 let out = &mut hole.dest;
1777 while *left < hole.end && right < v_end {
1778 // Consume the lesser side.
1779 // If equal, prefer the left run to maintain stability.
1780 let to_copy = if is_less(&*right, &**left) {
1781 get_and_increment(&mut right)
1783 get_and_increment(left)
1785 ptr::copy_nonoverlapping(to_copy, get_and_increment(out), 1);
1788 // The right run is shorter.
1789 ptr::copy_nonoverlapping(v_mid, buf, len - mid);
1792 end: buf.offset((len - mid) as isize),
1796 // Initially, these pointers point past the ends of their arrays.
1797 let left = &mut hole.dest;
1798 let right = &mut hole.end;
1799 let mut out = v_end;
1801 while v < *left && buf < *right {
1802 // Consume the greater side.
1803 // If equal, prefer the right run to maintain stability.
1804 let to_copy = if is_less(&*right.offset(-1), &*left.offset(-1)) {
1805 decrement_and_get(left)
1807 decrement_and_get(right)
1809 ptr::copy_nonoverlapping(to_copy, decrement_and_get(&mut out), 1);
1812 // Finally, `hole` gets dropped. If the shorter run was not fully consumed, whatever remains of
1813 // it will now be copied into the hole in `v`.
1815 unsafe fn get_and_increment<T>(ptr: &mut *mut T) -> *mut T {
1817 *ptr = ptr.offset(1);
1821 unsafe fn decrement_and_get<T>(ptr: &mut *mut T) -> *mut T {
1822 *ptr = ptr.offset(-1);
1826 // When dropped, copies the range `start..end` into `dest..`.
1827 struct MergeHole<T> {
1833 impl<T> Drop for MergeHole<T> {
1834 fn drop(&mut self) {
1835 // `T` is not a zero-sized type, so it's okay to divide by its size.
1836 let len = (self.end as usize - self.start as usize) / mem::size_of::<T>();
1837 unsafe { ptr::copy_nonoverlapping(self.start, self.dest, len); }
1842 /// This merge sort borrows some (but not all) ideas from TimSort, which is described in detail
1843 /// [here](http://svn.python.org/projects/python/trunk/Objects/listsort.txt).
1845 /// The algorithm identifies strictly descending and non-descending subsequences, which are called
1846 /// natural runs. There is a stack of pending runs yet to be merged. Each newly found run is pushed
1847 /// onto the stack, and then some pairs of adjacent runs are merged until these two invariants are
1850 /// 1. for every `i` in `1..runs.len()`: `runs[i - 1].len > runs[i].len`
1851 /// 2. for every `i` in `2..runs.len()`: `runs[i - 2].len > runs[i - 1].len + runs[i].len`
1853 /// The invariants ensure that the total running time is `O(n log n)` worst-case.
1854 fn merge_sort<T, F>(v: &mut [T], mut is_less: F)
1855 where F: FnMut(&T, &T) -> bool
1857 // Slices of up to this length get sorted using insertion sort.
1858 const MAX_INSERTION: usize = 20;
1859 // Very short runs are extended using insertion sort to span at least this many elements.
1860 const MIN_RUN: usize = 10;
1862 // Sorting has no meaningful behavior on zero-sized types.
1863 if size_of::<T>() == 0 {
1869 // Short arrays get sorted in-place via insertion sort to avoid allocations.
1870 if len <= MAX_INSERTION {
1872 for i in (0..len-1).rev() {
1873 insert_head(&mut v[i..], &mut is_less);
1879 // Allocate a buffer to use as scratch memory. We keep the length 0 so we can keep in it
1880 // shallow copies of the contents of `v` without risking the dtors running on copies if
1881 // `is_less` panics. When merging two sorted runs, this buffer holds a copy of the shorter run,
1882 // which will always have length at most `len / 2`.
1883 let mut buf = Vec::with_capacity(len / 2);
1885 // In order to identify natural runs in `v`, we traverse it backwards. That might seem like a
1886 // strange decision, but consider the fact that merges more often go in the opposite direction
1887 // (forwards). According to benchmarks, merging forwards is slightly faster than merging
1888 // backwards. To conclude, identifying runs by traversing backwards improves performance.
1889 let mut runs = vec![];
1892 // Find the next natural run, and reverse it if it's strictly descending.
1893 let mut start = end - 1;
1897 if is_less(v.get_unchecked(start + 1), v.get_unchecked(start)) {
1898 while start > 0 && is_less(v.get_unchecked(start),
1899 v.get_unchecked(start - 1)) {
1902 v[start..end].reverse();
1904 while start > 0 && !is_less(v.get_unchecked(start),
1905 v.get_unchecked(start - 1)) {
1912 // Insert some more elements into the run if it's too short. Insertion sort is faster than
1913 // merge sort on short sequences, so this significantly improves performance.
1914 while start > 0 && end - start < MIN_RUN {
1916 insert_head(&mut v[start..end], &mut is_less);
1919 // Push this run onto the stack.
1926 // Merge some pairs of adjacent runs to satisfy the invariants.
1927 while let Some(r) = collapse(&runs) {
1928 let left = runs[r + 1];
1929 let right = runs[r];
1931 merge(&mut v[left.start .. right.start + right.len], left.len, buf.as_mut_ptr(),
1936 len: left.len + right.len,
1942 // Finally, exactly one run must remain in the stack.
1943 debug_assert!(runs.len() == 1 && runs[0].start == 0 && runs[0].len == len);
1945 // Examines the stack of runs and identifies the next pair of runs to merge. More specifically,
1946 // if `Some(r)` is returned, that means `runs[r]` and `runs[r + 1]` must be merged next. If the
1947 // algorithm should continue building a new run instead, `None` is returned.
1949 // TimSort is infamous for its buggy implementations, as described here:
1950 // http://envisage-project.eu/timsort-specification-and-verification/
1952 // The gist of the story is: we must enforce the invariants on the top four runs on the stack.
1953 // Enforcing them on just top three is not sufficient to ensure that the invariants will still
1954 // hold for *all* runs in the stack.
1956 // This function correctly checks invariants for the top four runs. Additionally, if the top
1957 // run starts at index 0, it will always demand a merge operation until the stack is fully
1958 // collapsed, in order to complete the sort.
1960 fn collapse(runs: &[Run]) -> Option<usize> {
1962 if n >= 2 && (runs[n - 1].start == 0 ||
1963 runs[n - 2].len <= runs[n - 1].len ||
1964 (n >= 3 && runs[n - 3].len <= runs[n - 2].len + runs[n - 1].len) ||
1965 (n >= 4 && runs[n - 4].len <= runs[n - 3].len + runs[n - 2].len)) {
1966 if n >= 3 && runs[n - 3].len < runs[n - 1].len {
1976 #[derive(Clone, Copy)]